The present invention relates to the field of imaging distant targets.
There are many situations of practical military and intelligence importance where high-resolution images of distant objects are required but cannot be obtained by conventional imaging techniques. Factors such as atmospheric turbulence, internal optical aberrations, and vibration often prevent imaging systems from achieving diffraction-limited performance. It is known in the art, to illuminate a distant object or target with a narrow band laser pulse, which when scattered from the target forms a high quality speckle image pattern at the wavefront sensor aperture receiving returned light. The speckle pattern may be measured with respect to amplitude and phase using conventional interferometer techniques. If there were no aberrations due to the atmospheric or optical element distortion, the resulting wavefront pattern could be Fourier-transformed to produce a diffraction-limited target image. However, when aberrations are present, a severely degraded image will be produced and the effects thereof must be corrected before the transformation process takes place. Such a correction may be accomplished in real time by measuring the aberrations and removing them with an active electronically controlled deformable mirror. For certain applications however, it is desirable to replace the active optic correction systems with a system which enables extremely large-sized telescopes to be employed, which do not require precision optical elements, and can be made at surprisingly small expense. The elimination of the high cost, complexity, and power requirements of such active optical systems is a desired goal of the present invention.
It is thus an object of the present invention to enable the photographing of satellites or other objects through atmospheric turbulence, from large ground-based telescopes with high resolution.
It is a further object of the present invention to provide a method and means for producing high-resolution imagery from space-based telescopes subject to severe unknown aberrations, as may occur for example in space, where high-energy laser weapons systems are employed.
A further object of the present invention is to provide for the imaging of targets through atmospheric turbulence which results in very high quality images of the target, without the use of the relative costly and complex active optical element system for compensating for image distortion automatically.
It is yet a further object of the present invention to provide huge telescopes (perhaps 30 meters or more in diameter, which do not require precisely fabricated optical elements) for producing high-resolution images (in spite of possible turbulent viewing conditions) at relatively low cost.